1. Field of the Invention
The present invention is generally related to a fuel system for an internal combustion engine and, more particularly to a fuel injection system for an engine of an outboard motor in which a compressor crankcase is used to draw a vacuum which causes fuel to flow from a fuel tank to a fuel reservoir, such as a fuel vapor separator.
2. Description of the Prior Art
Many different types of fuel systems are well known to those skilled in the art of internal combustion engine design. Most fuel systems for internal combustion engines employ carburetion or fuel injection to provide fuel to a combustion chamber of the engine. In certain types of engines, such as fuel injected engines, a fuel vapor separator is used to separate liquid fuel from fuel vapor. In addition, in certain types of fuel injected engines, air compressors are used to provide a supply of pressurized air to assist in the injection of fuel into the combustion chambers of the engine.
U.S. Pat. No. 5,785,015, which issued to Phillippe et al on Jul. 28, 1998, discloses an internal combustion engine that is provided with a system for direct fuel injection with pneumatic assistance. The engine comprises a single piston compressor associated to each of the combustion chambers of the engine. The compressor draws an air/fuel mixture and, due to the action of its discharge stokes, injects the mixture directly inside the combustion chamber at an instant which is appropriately determined by the synchronization of the compressor. The discharge valve of the compressor is arranged inside the combustion chamber.
U.S. Pat. No. 4,241,711, which issued to Detweiler on Dec. 30, 1980, describes a fuel control system for a turbo charged engine. The system provides fuel delivered to the carburetor under the control of a vacuum operated device which is under the further control of a device which senses pressures upstream and downstream of the turbo charged compressor. It delivers a vacuum signal to the fuel control device in proportion to the manifold pressure even though the latter pressure may be a positive pressure.
U.S. Pat. No. 5,046,474, which issued to Percy on Sep. 10, 1991, described a crankcase ventilation and evacuation system. Crankcase fumes are treated by the apparatus which envisions a primary filtering system for extracting fuel, moisture and solids from the engine crankcase. The solids are mainly trapped by a filter element preventing reentry into the engine. The fuel vapors and moisture are conducted returnably to the engine for increasing horsepower and a secondary filtering system for secondarily for filtering the fuel vapors from solids before passage to the engine is also provided.
U.S. Pat. No. 4,142,494, which issued to Negri et al on Mar. 6, 1979, describes a turbo charged engine with a vacuum valve. The engine has a carburetor fuel metering control rod, an ignition timing control member, and exhaust gas recirculation control pintle, and an induction air temperature damper that is operated in response to vacuum signals created by the pressure in the induction passage between the throttle and the turbocharger compressor and a valve which bleeds the vacuum signals to atmospheric pressure when the compressor discharge pressure rises above a selected value to establish a rich air-fuel mixture, retard ignition timing, inhibit exhaust gas recirculation and provide a cool induction air flow for maximum power operation.
U.S. Pat. No. 4,878,475, which issued to Birsa on Nov. 7, 1989, discloses a fuel supply system for internal combustion engines. The fuel supply system is intended for use with internal combustion engines in which two different fuels are used, one to start the engine, to operate it at idling speed and to supplement the other fuel during acceleration, and the second to operate the engine at its normal working speed. The first fuel may be propane for starting, idling and for an acceleration supplement. The second fuel for normal working speeds, or normal driving speed may be gasoline. A first vacuum control valve assembly delivers the first fuel such as propane from a pressurized supply tank to the carburetor below the conventional butterfly valve of the throttle control to start the engine and operate it at idle speed. A second vacuum controlled valve assembly delivers the first fuel, such as propane, to the carburetor above the butterfly valve only when the accelerator opens the throttle and its butterfly valve to initiate acceleration, and only during acceleration. The second fuel such as gasoline which is used for the normal working or driving operation is supplied to the engine in the usual manner, from its supply tank to the carburetor by a fuel pump, and from the carburetor through the intake manifold to the combustion chamber by the vacuum created as the engine operates.
U.S. Pat. No. 4,635,606, which issued to Koike et al on Jan. 13, 1987, describes a fuel supply control system for internal combustion engines, capable of preventing vapor lock. The fuel supply control system for an internal combustion engine has fuel injection valves for supplying the engine with fuel and has its pressure regulated to a predetermined value. A temperature sensor detects a temperature value representative of the temperature of fuel being supplied to the fuel injection valves. When the temperature value detected by the sensor is higher than a predetermined value at the start of the engine, an electronic control unit causes a solenoid-operated selector valve to operate to increase the pressure of fuel being supplied to the engine over a period of time dependent on the temperature value detected by the sensor from the time the engine is started.
U.S. Pat. No. 4,386,593, which issued to Tibbs on Jun. 7, 1983, discloses a fuel-air air injection control system for internal combustion engines. The system is provided for internal combustion engines using gasoline as a fuel. The system includes a vacuum pump which is connected to an airtight fuel supply tank containing a liquid gasoline such that operation of the vacuum pump causes a portion of the liquid gasoline to become continuously vaporized. The vaporized but unheated gasoline is passed through a filter where unwanted contaminants are removed and the fuel is delivered to the intake ducts of the internal combustion engine. Heated air is also supplied to these intake ducts and the vaporized gasoline combines with heated combustion air therein for subsequent ignition in the combustion chambers. The flow of heated combustion air is controlled by the operator to control the speed of the engine.
U.S. Pat. No. 3,957,025, which issued to Heath et al on May 18, 1976, describes a method and apparatus for controlling displaced vapor emissions in motor vehicles. The vacuum emission control system is adapted to accommodate displaced vapors generated during the filling a motor vehicle storage tank, wherein a first storage tank is adapted to communicate sequentially with an intermediate vacuum accumulator and ultimately with the intake manifold of an internal combustion engine. In the preferred embodiment, a dispensing nozzle is inserted into vapor sealing engagement with a first liquid storage tank wherein the storage tank is equipped with a unidirectional self venting gas cap. Upon insertion of the dispensing nozzle a unidirectional bypass line normally closed is opened via an entry port flap actuator. A regulating negative pressure head draws the displaced liquid fuel tank vapors sequentially through a bypass valve, a first pressure regulator, a unidirectional check valve, a vacuum accumulator holding tank, a second unidirectional check valve which is also a flow regulator, a second pressure regulator, and finally into the intake manifold vacuum source of an internal combustion engine. An alternative embodiment is described wherein the liquid storage tank is vented directly to the atmosphere via conventional two way vent. In this embodiment, upon insertion of the dispensing nozzle, the entry port flap actuator closes the vent line which is normally open and simultaneously opens the normally closed unidirectional displaced vapor line to the vacuum accumulator.
One problem that occurs in certain types of internal combustion engines is an occasional inability to pump fuel, either from a fuel tank to a fuel reservoir or from the fuel reservoir to the combustion chambers of the engine. This problem can be seriously exacerbated in fuel injected engines which recirculate portions of the fuel from the injectors back to the fuel reservoir. This continued recirculation of bypass fuel raises the temperature of the fuel and increases the likelihood that the fuel will reach a temperature at which it will vaporize within the fuel delivery system. If the fuel vaporizes to a gaseous or vaporous state, certain types of pumps are unable to pump the fuel vapor. This condition is commonly referred to as vapor lock and usually occurs when the pump is insufficiently primed with liquid fuel because of the presence of fuel vapor. This problem can also occur within the pump which is used to draw fuel from a fuel storage tank and pump fuel to a fuel reservoir.
When the internal combustion engine is used in an outboard motor application, the bypass flow of fuel, which flows to the fuel injectors and is returned to the fuel reservoir without being injected into the combustion chambers, is not returned to the main fuel tank. Instead, because of safety concerns, the fuel is recirculated back to the fuel reservoir which is generally a fuel vapor separator. Under certain conditions, such as low speed operation, the majority of the fuel which is pumped to the fuel injectors is returned to the fuel vapor separator and this continuous recirculation by the pump raises the temperature of the fuel. The increased temperature of the fuel, particularly under warm ambient conditions, increases the likelihood that vapor lock can occur within the pump which pumps the fuel from the fuel vapor separator to the fuel injection system.
In outboard motor applications, the pump which draws fuel from the primary fuel tank and pumps it to the fuel vapor separator can also experience vapor lock. This is caused when the liquid fuel in the fuel line between the fuel tank and the fuel vapor separator is vaporized as a result of increased temperatures. The fuel in the fuel line can also be vaporized as a result of the reduced pressure at the inlet of a fuel pump as it attempts to pump the fuel from the primary fuel tank to the fuel vapor separator or other type of fuel reservoir. Therefore, vapor in the fuel system of an internal combustion engine can be caused by several conditions and can occur at several locations within the fuel system.
If vapor lock occurs in the fuel pump which draws fuel from the primary fuel tank and pumps it to the fuel vapor separator, the liquid level in the fuel vapor separator may be significantly lower because of the lack of additional liquid fuel pumped into the fuel vapor separator and also because of the fact that the high pressure fuel pump will continue to draw the liquid fuel from the fuel vapor separator and pump it to the fuel injection system. If the liquid fuel within the fuel vapor separator is drawn down to a sufficiently low level or if the fuel is of a sufficiently high temperature, the inlet of the high pressure pump can experience vapor lock and the fuel injection system will be deprived of fuel for the engine.
In view of the above described potential problems relating to a fuel injected engine, it would be significantly beneficial if a fuel system could be provided which does not require a pump to pump fuel from the primary fuel tank to the fuel vapor separator. It would be further beneficial if the fuel can be drawn from the primary fuel tank and conducted to the fuel vapor separator regardless of the fuel's temperature and regardless of the amount of fuel vapor in the fuel line with the liquid fuel.